1. Field
This invention relates to golf clubs, and more particularly to golf club irons, having a tri-weight system which improves the performance of miss hits on the club face and also reinforces the club face for center hits.
2. State of the Art
A large number of different golf club iron sets are known. Correlated sets of golf clubs have club striking faces with increasing angles of attack to loft a ball a desired distance. The club heads are also increasingly weighted, and the shafts are decreasingly shortened to maintain consistent swing momentum so that each club swing, if properly hit, decreases the distance the golf ball travels by approximately 10 yards. For example, in a correlated set, each club head weight generally increases approximately 7 grams per increase in club number. However, each shaft length incrementally decreases about ½ inch for a steel shaft per increase in club number. Shaft types and lengths vary depending upon the swing of a golfer. For example, the majority of golfers fall into the average swing category, and have a 65 to 85 mph swing speed requiring a shaft with a low flex point and approximately a 4.0 torque rating. Conversely, professional golfers having a 100 to 115 mph swing speed require a shaft with a mid or high flex point with a 2.0 or so torque rating.
The angle of the club face also increases per increase in the club number to add loft to the flight of the golf ball. The weighted center of gravity of the club also moves up along the hitting surface per increase in club number. A typical set has the following specifications:
SPECIFICATIONSClub123456789Loft  16°  18°  21°  24°  28°  32°  36°  40°  44°Lie*  56°  57°  58°  59°  60°  61°  62°  63°  64°Weight**223240247254261268275282289*Lie - plus or minus 0.5 degrees***Weight - plus 2 gr. or minus 2 gr.
Golf clubs are generally designed so that a golf ball hit by the club as the golfer swings the club should be hit at a point on the club face around the center of the club face, the center of percussion of the club, or the center of mass of the club. This is not necessarily the geometric center of the club, but is generally close to the geometric center. The club designer designs the club to provide this point which generally will be an area rather than a particular point, and may be referred to as the sweet spot of the club. The exact location of this point and the size of the area around this point where a golf ball can be hit and produce a properly hit or well hit golf ball varies with the design of the club. A shot that results in the golf ball going in the desired direction and for the expected distance is a properly hit or well hit shot. The area of the club face where the golf ball can be hit to produce the trajectory for a well hit shot for any particular club can be determined experimentally by use of a swing machine that swings a golf club in a consistent manner with a ball placed in a know position with respect to the club swing so the point of contact of the club face with the ball is known. By placing the ball to be hit at know different positions on the golf club face and determining the location where the golf ball lands, the sweet spot for the club can be determined. This sweet spot is the spot or area on the club face where a ball can be hit by the club face and produce a desired ball trajectory so that the ball will fall within an acceptable location in terms of distance and direction from the location from where the ball is hit. Depending on the particular club design, this sweet spot can be as large as a nickel or a quarter. This sweet spot on the club will be referred to as the most probable or the most likely hitting surface of the club, the portion or segment of the club most probably to impact the golf ball, or the most probable contact segment of the hitting surface.
The goal of every golfer is to consistently properly hit the golf ball, i.e., hit the ball in the center of the club. However, the challenge of golf is to consistently hit the ball in the center of the club. Most golfers will actually hit the ball in an area on the face of the club around the center of the club, but sometimes toward the toe of the club, the heel of the club, or above or below the center of the club. An off-center hit is when the golf ball hits the surface of the club between the center of the club and the toe of the club, the heel of the club, the top of the club, or the bottom or sole of the club. How far off center a hit is will determine how far from the desired direction and expected distance the ball will travel. Various club have been designed to enlarge the most probable hitting surface of the club face by providing various different patterns of weight distribution in the club. However, as mentioned, golf clubs are consistently weighted so if weight is added to one portion of a club, the same weight has to be subtracted from another portion of the club to maintain the same club weight.
A few golf club irons are designed to enable a golfer to off center hit the ball on the club face and maintain shot alignment. Thompson, U.S. Pat. No. 3,845,960, and Imal, U.S. Pat. No. 4,322,083, are examples of sole reinforced iron clubs which add mass along the sole of the club to optimize distance. Blakemore, U.S. Pat. No. 5,658,209 discloses a center reinforced mound placed in a cavity club. Best, U.S. D469,140S is another center reinforced mound placed in a cavity club. Although distance is increased, heel or toe off center hit shots do not maintain shot alignment. Nor do shots hit on the upper unreinforced face of the club maintain distance.
For those golfers who consistently hit their shots along the toe of the club, a number of toe weighted clubs have been designed: Lainanna, U.S. Pat. No. 4,715,601, Solheim, U.S. Pat. No. 3,655,188, and Campau, U.S. Pat. No. 4,420,156.
Solheim, U.S. Pat. No. 4,621,813, discloses a correlated set of golf clubs with back cavities, the heads of which each contain (1) a sole including a trailing edge which is indented toward the striking face a distance of at least 1/16 of an inch, and (2) a lower back surface adjacent the indented trailing edge sloping upwardly and inwardly from the indented trailing edge toward the striking face. This configuration allows the club head material, which would otherwise be located in the indented areas to be redistributed in the heel and toe portions of the club heads. The redistributed head materials increase the mass concentrations in the heel and toe areas, which improves the resistance to twisting of the club heads upon off-center heel and toe impacts with the golf ball. Another example of a back cavity club with heel and toe reinforcement is Lockwood, U.S. Pat. No. 3,751,035, Kobayashi et al., U.S. Pat. No. 5,564,705, and Persinger, U.S. D437,902S. The center cavity club designs maintain alignment, but do not allow an off center hit shot to maintain consistent distance. Nor do center hit shots achieve optimum distance as the center face of the club does not have sufficient mass behind it.
Antonious, U.S. Pat. No. 6,454,665B2 included unique weighting stabilizing and reinforcing configuration of the rear face of a cavity back peripheral weight club head in an attempt to remove this well hit shot distance deficiency. Peng, Des. 413,369 and Takahashi et al, Des. 377,381 also attempted to include center weights within the cavity to remove this distance deficiency.
McNally et al., U.S. Pat. No. 5,026,056, discloses another heel-toe balancing club. McNally et al. discloses a correlated set of golf clubs of the iron type in which each club head has a cavity formed in the back surface thereof with specially configured weight pads formed integrally within the back cavity. The weight pads are so configured and positioned within the back cavity as to create desired heel-toe balancing of each club head wherein each club head's center of gravity is physically centered, both horizontally and vertically of the club head, behind the visually-perceived optimal striking point, i.e., the apparent visual center of percussion of the club's striking face relative to the golf ball at address. This configuration is designed to provide better club balance, and minimize misdirection of heel or toe off center hit shots. Other examples of heel-toe balancing clubs are: Reymann, Jr. et al., U.S. Pat. No. Des. 269,101, Solheim, U.S. Pat, No. Des. 276,644, and Solheim, U.S. D458,328S, which also includes a sole center weight in the cavity.
These cavity backed clubs do not provide a solid mass behind the club face center to maximize hitting distances. To overcome this lack of center of mass, the Merit Fusion/Nicklaus Nl provides a set of correlated golf clubs with an iron weight bar placed within the inside of the back cavity which can be adjusted vertically to promote vertical balancing for an exact center of gravity as well as provide additional mass behind the club face. MacDonald, U.S. Pat. No. 4,326,326 is another example of a lead insert golf club head positioned directly behind the center of the intended striking surface to improve distance. Other examples of center reinforced golf club heads are: Winquist, U.S. Pat. No. 3,814,437, Kobaynshi, U.S. Pat No. Des. 267,965, Pace, U.S. Pat. No. Des 268,775, and Aizawa et al., U.S. Pat. No. 5,547,194. Katayama, U.S. Pat. No. 5,160,137 discloses a bubble weighted club with rearward projecting sole. Gorman, U.S. Pat. No. 5,048,834 discloses a center mound weight within the cavity, but is a flat piece not including any periphery weighting reinforcement. Wahl et al., U.S. D444,195S discloses a club with a center weight reinforcement cavity design.
Unfortunately, these center reinforced cavity configurations also raise the center of gravity of the club face, thereby reducing the mass along the lower center of the club face proximate the sole where maximum leverage striking force for an iron shot is delivered. Indeed, the Pace design actually raises the center of gravity. Ming T. Chen and Jeffrey R. Thurman patented a dual weighted iron golf club, which included perimeter weights designed to straighten miss hit iron shots, and a center weight within the back of the cavity behind the club face to provide added distance to properly hits shots in U.S. Pat. No. 5,356,138. Claim 1 of said patent was invalidated in the DISTRICT OF UTAH, CENTRAL DIVISION PRO SPORTS, USA, vs. MIZUNO USA-Golf Division, Case No. 2:98-CV-866-S by the Honorable Ted Stewart who interpreted claim 1 to require that the center mound weight was positioned above the thickness of the sole and was therefore anticipated by certain references.
Bode et al., U.S. D 468,788S discloses another dual weight iron club similar to Chen with a rear projecting sole. Mahaffey et al., U.S. D454. 932 S discloses another iron club with a rearward projecting thickened combination sole/center weight. Helmstetter et al., U.S. D453,949S discloses another iron club with a complex cavity back design
Erickson et al., Des 435,277 discloses a cavity backed club with a thickened combination sole/center weight which does not project rearward. Erickson et al., U.S. Pat. No. 6,554,722B2 discloses a bi-material weight added to the design of Des. 435,277. Imamoto, U.S. D466,960S discloses a club similar to Erickson et al., with an added center portion.
There are other solid backed clubs still used by professionals and other golfers with consistent swings, who consistently hit the ball in the center of the club face to acquire consistent optimum distance and loft. As most golfers do not have a consistent swing, and often miss hit the ball, various manufacturers started developing wider club heads for their needs. To insure that the club heads still had the same weight, these manufacturers developed hollows or cavities in the back of the club to spread the weight over a wider club head in essentially two types of patterns: 1) muscle backed clubs with center weights mounted behind the hitting surface on the back without a cavity, and 2) perimeter weighted clubs with weights behind the heel and toe on both sides of the cavity behind the club hitting surface. The muscle backed clubs did not straighten out miss hit shots striking the heel and toe of the club. Conversely, the perimeter weighted clubs self corrected miss hit shots on the heel and toe of the club, but lacked center weight to add distance to properly hit center struck shots.
Aizawa et al., U.S. Pat. No. 5,616,088 discloses a golf club head with rearward extending upper and lower flanges on the peripheral backside of a club head projecting rearwardly to enhance the moment of inertia and improve direction stability of a ball.
Other patents of interest are: Soheim, U.S. Pat. No. 4,512,577, discloses a set of correlated golf clubs, the heads of which are provided with a narrowed neck connecting the main body of the club head to the hosel. The midsection of the neck has a cross section of maximum dimension less than the diameter of the hosel so that, when the main body of the club head twists under impact with a ball, the narrowed neck will function as a torsion bar with twisting tension occurring in the mid-section. In that manner, the twisting motion of the main body is uncoupled from the hosel and shaft to provide a more forgiving shock absorbing club head in the event an iron shot is miss hit This shock absorbing feature does not give consistent distance to a miss hit ball.
Moser, U.S. Pat. No. 3,250,536, is an example of a sand wedge with a reinforced weighted club having a different density filling material filling a cavity in the back of the club to balance the club.
Kenmi, U.S. Pat. No. 5,913,735 disclosing a metallic golf club head having a hollow head body with a sole member formed on an interior surface of the sole member.
Vincent et al., U.S. 2003/0013545A1 discloses a golf club iron having a sole with recesses into which different inserts may be inserted to dissipate vibration.
Takeda, U.S. Pat. No. 5,976,033 discloses a golf club with structure for securing balancing weights to the back of the club head.
Deshmuky et al., U.S. Pat. No. 6,406,382B1 discloses a golf club with a multiple material weighting member using liquid phase sintering, preferably a high-density component, a binding component and an anti-oxidizing component.
Kusumoto et al, U.S. 2003/0114245A1 discloses a golf club head containing 15 wt. % or greater of iron and tungsten, and having a specific gravity of 9 or larger joined to a steel or pure iron head body by welding.
There thus remains a need for a rear cavity weighted club which maintains a low center of gravity while providing additional mass behind the center most likely segment of the striking surface of the club to optimize shot distance and move the center of gravity of the club rearward to assist in maintaining alignment even though the shot is off center hit near the toe, heel, or upper segment of the club face. The golf club set described below provides such an invention.